Florida's two U.S. senators say the nightclub shooting in Orlando that appears to be the nation's worst in history, appeared to be related to radical Islamic terrorism.

“Right now there’s a lot of indications that this has some link to radical Islam,” Republican Sen. Marco Rubio told CNN on Sunday. “I think we have to continue to explain to people, this is the new face of the war on terror. … And it’s a reminder that the war on terror has evolved into something that we never had to confront before.”

President Barack Obama, speaking about 12 hours after the shooting began, said, "We know enough to say this was an act of terror and an act of hate," and added that his administration will "resolve to defend our people."

Obama used his remarks to make yet another call for tighter gun laws, calling it a "further reminder how easy" it is for someone to obtain powerful firearms.

"We have to decide if that’s the kind of country we want to be," he said. "To do nothing is a decision, as well."

House Intelligence Ranking Member Adam Schiff, D-Calif., told CNN that local law enforcement indicated the shooter in the Orlando attacks had made a pledge of allegiance to the Islamic State.

"What I heard from Department of Homeland Security this morning is, according to local police, he made a pledge of allegiance to ISIL, was heard praying in a foreign language," Schiff said. "And I don't know if this was at some point during the course of the shooting, but that's I'm hearing, obviously second-hand, coming ultimately from local police."

House Intelligence Chairman Devin Nunes of California told CNN that he was not jumping to any conclusions, but, “From my experience, this looks like radical Islam.”

“Clearly radical islam wants to target the gay community,” Nunes said. “And this would be a prime location to do that.”

Sen. Bill Nelson, a Democrat, encouraged anyone with information about the shooter to come forward.

Officials identified the gunman as Omar Mateen, a 29 year-old Florida resident. Law enforcement officials say Mateen opened fire inside the Pulse, one of Orlando’s largest gay nightclubs, at 2 a.m., and was killed by officers when they stormed the building at around 5 a.m.

Nelson told CBS’ Face the Nation that he was in touch with federal officials, who were following “the trail of Islamic radicalism.”

Earlier Sunday, New York GOP Rep. Peter King told CNN, “He was from Afghanistan and was trained in the use of weapons — that’s as far as I’ll go.”

The attack was the deadliest mass shooting in U.S. history, with the death toll surpassing the 2007 shooting at Virginia Tech, in which 32 were killed.

Though officials are classifying the shooting as a terror incident, Sen. Christopher S. Murphy called on Congress to act to prevent further mass shootings.

“Congress has become complicit in these murders by its total, unconscionable deafening silence,” the Connecticut Democrat said in a statement Sunday. “This doesn't have to happen, but this epidemic will continue without end if Congress continues to sit on its hands and do nothing — again.”

The White House said President Barack Obama has been briefed on the situation and will receive regular updates. Vice President Joseph R. Biden Jr. announced Sunday that he would no longer attend a planned fundraiser for Democratic National Committee Chairwoman Debbie Wasserman Schultz.

A spokeswoman for Washington, D.C.'s Metropolitan Police Department told CQ Roll Call that it is increasing security around the District's Pride Festival on Sunday following the Orlando shootings.